1. Field of the Invention
The present invention relates in general to the field of laparoscopic surgery, and more particularly to a system and method for detection and mapping of internal nerve tissue.
2. Description of the Related Art
Traditionally, surgery on internal body parts is performed by cutting an incision in the skin to access the internal body parts. Such open surgery entails a number of known risks including infection, inadvertent damage to other organs and structures, scarring, and loss of blood. In an effort to reduce some of these risks and improve patient outcomes surgeons have developed laparoscopic, and more recently robotic, techniques to perform surgery. Robotic surgery is essentially an advanced type of laparoscopic surgery in which the arms that enter the body cavity are robotically controlled instead of manually controlled. During a laparoscopic or robotic surgery, small incisions are made in the skin through which 5-12 millimeter access ports are placed. These ports serve as doorways through which small working instruments and a camera can be placed. The camera creates a magnified view of the internal organs that the surgeon sees on a monitor or console. Such less invasive laparoscopic and robotic surgeries typically have reduced side effects for the patient to allow a more rapid and complete recovery.
One example where laparoscopic and robotic surgery has gained acceptance with positive results is for the accomplishment of a radical prostatectomy. Conventionally, a radical prostatectomy is performed by cutting an incision at the base of the pelvic bone to gain access to the prostate. Once visible, the prostate is cut from the surrounding tissue and removed. Because the area around the prostate is rich in nerves and muscles that support sexual and urinary functions, a radical prostatectomy can cause severe side effects, including sexual dysfunction and incontinence. For example, up to half of conventionally-performed radical prostatectomies result in permanent erectile dysfunction. In contrast, a radical laparoscopic or robotic prostatectomy has the potential for far fewer side effects. In part, laparoscopic and robotic prostatectomies tend to have fewer side effects because the procedure affords the surgeon improved vision and in the case of robotics in particular, more dexterous tools as well. In the case of robotic surgery the improved vision and dexterity of the tools permits a skilled surgeon to better preserve sexual function nerves with as few as ten percent of patients being impotent as a result.
Although laparoscopic and robotic surgery has shown promising potential in reducing erectile dysfunction as a side effect of prostate gland removal, erectile dysfunction does still occur. In some instances, erectile dysfunction after a laparoscopic or robotic prostatectomy cannot be prevented due to Wallerian degeneration of nerves after even a slight injury. However, in some cases erectile dysfunction results from inadvertent damage done to the neurovascular bundle (NVB) that supports erectile function because the NVB is not where the surgeon expects. Direct visualization and appearance of the presumed NVB has not traditionally been a good indicator of preserved erectile nerves. The NVB travels from the base of the prostate where it joins with the bladder, to the apex (the portion where the urethra enters the penis). These nerves travel on opposing sides in a symmetrical fashion on the outside of the prostate capsule on its undersurface at the four and eight o'clock positions. Previous attempts at nerve monitoring during radical prostatectomy used electrical stimulation along the NVB with measurement of the signal in the cavernous bodies via a measurement of intracavernous pressures, i.e., muscle response to electrical stimulation. This method is not time efficient and recent studies have indicated that outcomes are inconsistent with the intraoperative findings.